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Abstract:

Improving the accuracy of the flow rate of a valve in a fluidic delivery
device in which a desired flow rate may be achieved by varying the duty
cycle of the valve. The flow rate of fluid delivery from the valve over
its lifetime is stabilized by minimizing the voltage OPENING time of the
valve to account for valve and piezoelectric actuator drift. Also, the
valve OPENING time of one or more fluidic parameters that impact on the
flow rate delivery by the valve and differ among fluidic delivery devices
is compensated to optimize the flow rate accuracy.

Claims:

1. A valve assembly with variable flow rate of fluid delivery,
comprising: a power supply; charge pump circuitry powered by the power
supply; wherein the charge pump circuitry includes at least one switch,
at least one inductor and at least one diode; a piezoelectric actuator
charged by the charge pump circuitry, the charge applied across the
piezoelectric actuator reaching a predetermined voltage threshold over a
predetermined rise time; and a valve transitioning from a CLOSED state to
an OPENED state when the charge applied across the piezoelectric actuator
exceeds the predetermined voltage threshold; the valve transitioning from
the OPENED state to the CLOSED state by discharging the applied charge
across the piezoelectric actuator; the valve assembly having a duty
cycle.

2. A method for varying a flow rate of fluid delivery, comprising the
steps of: applying a charge across a piezoelectric actuator via charge
pump circuitry powered by a power supply, a valve transitioning from a
CLOSED state to an OPENED state when the charge applied across the
piezoelectric actuator exceeds a predetermined voltage threshold; wherein
the charge pump circuitry includes at least one switch, at least one
inductor and at least one diode; discharging the applied charge across
the piezoelectric actuator to transition the valve from the OPENED state
to the CLOSED state; varying the flow rate of the fluid delivery from the
valve by adjusting a duty cycle of the valve.

3. The valve assembly in accordance with claim I, wherein the duty cycle
is adjusted to vary the flow rate; and the duty cycle represents a ratio
of valve OPENED time to valve CLOSED time.

4. The method in accordance with claim 2, wherein the duty cycle
represents a ratio of valve OPENED time to valve CLOSED time.

5. The valve assembly in accordance with claim 1, wherein the at least
one switch is a transistor.

6. The method in accordance with claim 2, wherein the at least one switch
is a transistor.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation application of U.S. patent
application Ser. No. 12/255,662, filed Oct. 21, 2008, which is herein
incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention is directed to a system and method for
improving the flow rate accuracy of a fluidic delivery system.

[0004] 2. Description of Related Art

[0005] Fluidic delivery devices have widespread use in the medical field
with the use of implantable drug infusion delivery devices for delivering
a drug or other fluid to the body at specified flow rates over time. The
implantable drug infusion delivery device is generally programmed via a
control unit disposed external to the body and in communication with the
implantable drug infusion delivery device via a communication interface,
preferably a wireless communication interface such as RF telemetry. There
are many types of drug infusion delivery devices or pumps such as
peristaltic, bellows, piston pumps. U.S. Patent Application Publication
No. 2007/0090321 A1 discloses one exemplary piston pump, which is herein
incorporated by reference in its entirety.

[0006] With the advent of such technology, it is possible to program a
specific drug profile over time to be dispensed or delivered from the
implantable drug infusion delivery device. Such functionality may be used
for dispensing a wide range of drugs such as pain medication or the
delivery of insulin as well as many others. Despite the advantages
associated with using an implantable drug infusion delivery device to
automatically dispense a drug over time based on a programmed drug
delivery profile, its efficacy depends on the ability of the implantable
drug infusion delivery device to dispense the medication at a
substantially constant flow rate on which the programmed drug delivery
profile was based. Otherwise, if the flow rate of fluid dispensed by the
drug infusion delivery device varies over time then the programmed drug
delivery profile will result in either an underdosage or an overdosage.
Any deviation in the drug dispensed may have unintended if not harmful,
and in some cases life threatening, health effects for the patient.

[0007] It is therefore desirable to develop an improved system and method
for stabilizing the flow rate of a fluidic delivery device over its
lifetime and also to optimize the flow rate accuracy of a fluid delivered
from a fluidic delivery device to compensate for one or more fluidic
parameters that compromise the flow rate.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to a system and method for
improving the accuracy of the flow rate of a valve in a fluidic delivery
device in which a desired flow rate may be achieved by varying the duty
cycle of the valve. The flow rate of fluid delivery from the valve over
its lifetime is stabilized by minimizing the voltage OPENING time of the
valve to account for valve and piezoelectric actuator drift. Also, the
valve OPENING time of one or more fluidic parameters that impact on the
flow rate delivery by the valve and differ among fluidic delivery devices
is compensated to optimize the flow rate accuracy.

BRIEF DESCRIPTION OF THE DRAWING

[0009] The foregoing and other features of the present invention will be
more readily apparent from the following detailed description and
drawings of illustrative embodiments of the invention wherein like
reference numbers refer to similar elements throughout the several views
and in which:

[0010] FIG. 1a is a perspective view of a valve assembly 10 for a fluidic
system;

[0011] FIG. 1b is a cross-sectional view of the valve assembly of FIG. 1a;

[0012] FIGS. 2a-2c show different exemplary flow rates for a valve
assembly having a block of 400 seconds by varying the duty cycle in
accordance with the present invention;

[0013] FIG. 3a is an exemplary graphical representation of the actual
valve OPENED and valve CLOSED timing of the valve assembly in FIG. 1b
over time;

[0014] FIG. 3b is an exemplary graphical representation of the discharge
signal for discharging of the piezoelectric actuator;

[0015] FIG. 3c is an exemplary graphical representation of the
piezoelectric actuator voltage;

[0016] FIG. 3d is an exemplary graphical representation of the PWM charge
input signal to the charge pump circuitry in FIG. 4 wherein the PWM
charge input signal has been divided into 20 PWM units each having its
associated PWM parameters;

[0020] FIGS. 3k-3n represent waveforms depicting valve state, discharge
signal and actuator voltage signal associated with an exemplary second
valve OPENING time greater than the first valve OPENING time depicted in
FIGS. 3g-3j;

[0021] FIG. 4 is an exemplary schematic circuit diagram for generating a
PWM charge input signal to achieve a predetermined threshold voltage of
60V across the piezoelectric actuator in FIG. 2 and open the valve;

[0022] FIG. 5 shows an exemplary single PWM charge input signal generated
for a single block of 400 seconds duration at a constant power supply
voltage, wherein the PWM charge input signal is subdivided into 20 PWM
units and varying the OFF time of the transistor in FIG. 4 while the
transistor ON time remains constant;

[0023] FIG. 6 shows exemplary PWM units over a period of time (e.g.,
several years) for depicting a decreasing power supply voltage, wherein
the ON time of the transistor in FIG. 4 is varied while the transistor
OFF time remains constant;

[0024] FIG. 7 is a graphical representation of the weight of fluid
delivered by a fluidic delivery device over time without taking into
consideration the compliance effect of the seal;

[0025] FIG. 8 is a graphical representation of the weight of fluid
delivered by a fluidic delivery device over time showing the compliance
effect produced by the seal;

[0026] FIGS. 9a-9g show as an illustrative example of the compliance
effect on an air bubble trapped in a valve as it opens and closes;

[0027] FIG. 10 is an exemplary flow chart depicting the process in
determining the Total Compensated Valve OPENING Time Per Block to
compensate for one or more of the calibrated fluidic parameters; and

[0028] FIG. 11 is an exemplary schematic diagram of an external control
device used to program an implantable drug delivery device and the
specific memory architecture within the implantable drug delivery device.

DETAILED DESCRIPTION OF THE INVENTION

[0029] FIGS. 1a and 1b depict a valve assembly 10 for use in a fluidic
system, e.g., implantable drug infusion delivery system. Valve assembly
10 has a body 12 which defines a bore 14 that is sized and shaped to
slidably receive a piston 16, as shown in the cross-sectional view of
FIG. 1b. Body 12 further includes an inlet passage 18 that provides fluid
communication between a fluid reservoir 62 and a lower end 20 of bore 14.
In addition, body 12 includes an outlet passage 22 for transporting fluid
from the valve assembly 10 (when the valve is in an OPEN state) to a
conduit that delivers the fluid to a desired site of interest.

[0030] In this exemplary valve structure or assembly 10, piston 16 is
positioned within bore , 14 and includes an upper sealing end 24 that
supports a disc-shaped seal 26. Piston 16 has an opposite lower end 28,
which includes a downwardly-directed boss 30 sized and shaped to receive
one end of a compression spring 32. In addition, piston 16 has defined
therein a circumferentially disposed spiral groove 34 (positioned along
the sidewall and extending substantially the length of the piston 16)
providing fluid communication between the lower end 20 of bore 14 (and
inlet passage 18) and upper sealing end 24 of piston 16. Fluid entering
the lower end 20 of bore 14 (under pressure from the reservoir 62) freely
advances between the piston 16 and the bore 14 via spiral groove 34.

[0031] As shown in FIG. 1b, spring 32 is positioned between lower end 28
of piston 16 and the lower end 20 of bore 14. Spring 32 biases piston 16
and disc-shaped seal 26 upwardly towards an upper end 36 of bore 14.

[0032] Securely attached (i.e., preferably hermetically sealed) to body 12
and positioned over upper end 36 of bore 14 is a contact disc 38 that is
preferably made from a rigid material such as a metal. Contact disc 38
has a central opening 40 defined therein and an integrally formed,
downwardly-directed contact ridge 42. Contact ridge 42 is formed
preferably concentrically to central opening 40 and sized and shaped to
fit within bore 14, as shown in FIG. 1b. Contact disc 38 is positioned so
that contact ridge 42 aligns with disc-shaped seal 26. As piston 16 is
pushed upwardly by spring 32, disc-shaped seal 26 is pressed into a
sealing contact with circular contact ridge 42 thereby closing the valve
assembly 10, as described in greater detail below.

[0034] Securely affixed to body 12 (i.e., preferably hermetically sealed)
and positioned over upper end 36 of bore 14 and contact disc 38 is a
portal support ring 44 which includes a central opening 46 and defines a
lower surface 48. Attached to the lower surface 48 and covering the
central opening 46 is a thin, flat coin-like, flexible membrane 50
positioned above an upper surface 52 of contact disc 38 a predetermined
distance so that a collection space 54 is defined therebetween.

[0035] Membrane 50 is generally made from a relatively strong resilient
metal such as titanium and is brazed or welded to the lower surface 48 of
portal support ring 44. Similarly, portal support ring 44 is brazed to
body 12 so that piston 16, disc-shaped seal 26, spring 32, inlet passage
18, outlet passage 22, and contact disc 38 all define a "wet side"
relative to membrane 50 (lower side) and are all hermetically sealed
within the valve body 12 yet isolated from everything located above and
outside the valve body 12 by a space which defines a "dry side" relative
to membrane 50. Upper surface 27 of contact pin 25 abuts against a lower
surface 51 of membrane 50. Spring 32 biases contact pin 25 into firm
contact with lower surface 51 of membrane 50.

[0036] The valve assembly 10 is opened and closed repeatedly at a
predetermined frequency by applying the mechanical displacement generated
by a piezoelectric actuator or piezo crystal 53 (in response to an
applied electrical signal) to move piston 16 axially up and down. An
actuation pin 55 is used to connect the piezoelectric actuator 53 to
contact pin 25 indirectly through membrane 50, as described below.
Actuation pin 55 is substantially axially aligned with contact pin 25.

[0037] In operation of the above described valve assembly 10, fluid (e.g.,
a drug in liquid form) is supplied to inlet passage 18 under pressure
from a reservoir 62, but regulated by a fluidic pressure regulator or
fluidic restrictor 60 such as a fluidic chip. Fluid enters lower end 20
of bore 14. When piston 16 is forced downwardly within bore 14 against
the action of spring 32 fluid from the reservoir 62 passes through the
fluidic pressure regulator 60 and into the inlet passage 18 moving past
piston 16 by way of groove 34 to the top of piston 16. Downward
displacement of piston 16, in turn, causes disc-shaped seal 26 to
separate from contact ridge 42 thereby allowing fluid (still under
regulated pressure) to pass through central opening 40 defined in contact
disc 38 and enter the collection space 54. Any fluid within collection
space 54 will be forced into outlet passage 22 and eventually directed to
a desired site of interest (such as a desired treatment area of a
patient's body).

[0038] Downward movement of piston 16 is controlled by applying a specific
electrical signal to the piezoelectric actuator 53 that as a result
thereof deforms with a slight downward displacement. This slight downward
movement is transferred to the contact pin 25 through the actuation pin
55 and flexible membrane 50. Therefore, the particular electric signal
applied to the piezoelectric actuator 53 will indirectly control the
opening of the valve assembly 10 and therefore the amount and flow rate
of fluid passing from inlet passage 18 to the outlet passage 22.

[0039] The flow rate of the fluid being dispensed from the outlet passage
22 is adjustable by varying the ratio of the valve OPENED time/valve
CLOSED time (ratio of the duration of time in which the valve is in
respective OPENED and CLOSED states) of the valve assembly 100 by means
of the piezoelectric actuator 53. Pressurized reservoir 62 is fluidly
connected to the fluidic regulator or restrictor 60. The outlet of the
flow regulator or restrictor 60 is, in turn, fluidly connected via an
inlet passage 18 to the bore 14 in which piston 16 is displaceable
thereby opening and closing the valve. While in an OPENED state fluid is
permitted to pass through the valve assembly 10 and dispensed via the
outlet passage 22. When the valve assembly 10 is in an OPENED state, the
fluidic restrictor 60 and the differential pressure across it define a
constant flow rate at the outlet passage 22 of the fluidic delivery
system.

[0040] The constant flow rate dispensed from the valve assembly can be
adjusted, as desired, by varying the ratio of the valve OPENED time to
the valve CLOSED time hereinafter referred to as the duty cycle. During a
predetermined period of time or duration (hereinafter referred to as a
"block") the valve assembly opens once (the piezoelectric actuator is
charged) and the valve closes once (the piezoelectric actuator is
discharged). Knowing the predetermined block duration (e.g., 400
seconds), the flow rate for the valve assembly can be determined based on
the duration of the valve OPENED time versus the valve CLOSED time.

[0041] FIGS. 2a-2c depict different flow rates, e.g., 4 ml/day, 2 ml/day
and 1 ml/day, respectively. A maximum constant flow rate of 4 ml/day is
represented in the first example shown in FIG. 2a in which for each 400
second block the valve OPENED time is the virtually the full 400 seconds,
while the valve CLOSED time is extremely short, almost zero (as denoted
by the enlarged view of the first 400 second block). The second example,
shown in FIG. 2b shows for each 400 second block the valve OPENED time
and the valve CLOSED time are equally 200 seconds duration each. This
would result in a flow rate half that of the maximum flow rate (e.g., 4
ml/day shown in FIG. 2a) for a constant flow rate of 2 mL/day. A third
example is depicted in FIG. 2c in which the valve OPENED time is for 100
seconds while the valve CLOSED time is 300 seconds. The third duty cycle
example will produce a constant flow rate of 1 ml/day. By varying the
duty cycle (i.e., the ratio of the valve OPENED time to the valve CLOSED
time) a desired constant flow rate of fluid dispensed from the valve may
be realized.

[0042] FIG. 3a is an exemplary graphical representation of the opening and
closing over one hour of valve assembly 10 in FIGS. 1a and 1b. There are
a total of 9 blocks within one hour depicted in FIG. 3a, each block being
400 seconds. The smallest time interval over which the valve can be
programmed by a user is 1 hour increments. Each 400 second block
comprises a valve OPENED time and a valve CLOSED time of equal duration
(e.g., 200 seconds). By way of example, the maximum flow rate defined by
the flow restrictor 110 and the differential pressure across it is 2
ml/day. This example is merely for illustration purposes and any one or
more of the parameters, may be selected as desired, including: (i) the
duration or time period of the block (e.g., 400 seconds), (ii) minimum
programming period of time (for example, one hour), (iii) maximum flow
rate in a 24 hour period, (iv) valve OPENED time, and (v) valve CLOSED
time.

[0043] Valve assembly 10 is a mechanical device that forms a fluid channel
capable of being either opened or closed by a piezoelectric actuator 53.
When actuated the piezoelectric actuator 53 bends and moves the plunger
or piston 16 downward via actuation pin 55. As a result, the valve opens.
A predetermined threshold voltage of 60 V (as denoted by line 301 in FIG.
3c) is needed to be applied across the piezoelectric actuator in order to
open the valve assembly 10. The voltage across the piezoelectric actuator
53 is supplied by power supply (e.g., a battery) and associated charge
pump circuitry an example of which is shown in FIG. 4.

[0044] Circuitry 600, in FIG. 4, is used to charge the piezoelectric
actuator 53 to the predetermined threshold voltage of 60V that, in turn,
opens the valve assembly 10 (in FIG. 1b). Power supply 605, for example,
a battery is used to power circuitry 600. The battery may be a
rechargeable battery or a non-rechargeable battery. As represented by the
shaded PWM charge input signal 307 in FIG. 3d, the piezoelectric actuator
53 is charged once every block (e.g., 400 seconds) regardless of the flow
rate, therefore the lifetime of the power supply is independent of the
flow rate. A capacitor 610 is connected in parallel with power supply
605. Transistor 620, for example a Field Effect Transistor (FET) is
periodically switched ON and OFF in response to receiving a Pulse Width
Modulated (PWM) charge pump input or driving signal generated by
processor 640 to allow energy received from the power supply 605 and
stored in an inductor 615 to charge the piezoelectric actuator 53.

[0045] Voltage Scaling Circuitry 625 scales down the relatively high
measured voltage or charge stored by the piezoelectric actuator 53,
preferably by a factor of 40, and generates a Measured Piezoelectric
Voltage Feedback Signal that is received as input to the processor 640. A
comparison is made by an analog comparator comprising processor 640
between the scaled down Measured Piezoelectric Voltage Feedback Signal
and a similarly scaled down predetermined stored reference voltage of
1.2V (representing the predetermined threshold voltage of 60V scaled down
by the same factor of 40 as that of the Measured Piezoelectric Voltage
Feedback Signal) for actuating the piezoelectric actuator 53. If the
scaled down Measured Piezoelectric Voltage Feedback Signal is less than
1.2V then the PWM charge pump input signal is generated causing the
transistor 620 which receives it to switch ON and OFF and allow the
stored charge in inductor 615 to be applied to the piezoelectric actuator
53. The Measured Piezoelectric Voltage Feedback signal is continuously
monitored until it reaches 1.2V at which point processor 640 triggers an
interrupt that cuts off the PWM charge pump input signal causing
transistor 620 to switch OFF permanently thereby opening the circuit and
preventing the flow of energy from the power supply 605 to the inductor
615. Accordingly, energy from the power supply 605 is only consumed
during charging of the piezoelectric actuator 53 until reaching the
predetermined threshold voltage of 60V. Once the valve is open (i.e., the
piezoelectric actuator is charged to the predetermined threshold voltage
of 60V) it is maintained opened (i.e., the piezoelectric actuator
substantially retains its charge with relative small leakage over time
(represented by the drop in voltage over the time represented by
reference element 308 in FIG. 3d) due to relatively low leakage diodes D1
and D2) without requiring energy. At the end of the valve OPENED time
(represented by each "OPENED" block in FIG. 3a), processor 640 generates
a Disable Signal or Discharge Signal (shown in FIG. 3b) that is received
as input by Voltage Discharge Circuitry 630 to discharge the charge built
up across the piezoelectric actuator 53 from the predetermined threshold
voltage of 60V (represented by reference element number 301) down to the
valve OPENING voltage 302 that differs among fluidic delivery devices.
Thus, the only negligible energy expended to discharge the piezoelectric
actuator 53 and close the valve is the power required by the processor to
generate the discharge pump signal and the energy dissipated by the
transistor when switching its state.

[0046] The input of the charge pump circuitry is a PWM signal, such as the
exemplary PWM signal shown in FIG. 3d. The output of the charge pump
circuitry is the voltage applied across the piezoelectric actuator 53 as
shown in FIG. 3c. It will take a predetermined period of time represented
by reference element 307, referred to as rise time, for the voltage
applied across the piezoelectric actuator 53 to attain the predetermined
threshold voltage of 60V necessary to open the valve 115.

[0047] Over the lifetime of the valve assembly the valve OPENING voltage
(reference element 302 in FIG. 3c) for a particular valve will increase
due to drift of the piezoelectric actuator behavior. For instance,
initially at the time of implantation, a valve may have a valve OPENING
voltage of 55V and after the passage of a period of time, for example,
several years, the valve OPENING voltage may rise to 57V. Variation in
the valve OPENING voltage over the lifetime of the valve assembly will
result in undesirable deviation in the accuracy of the programmed flow
rate of the fluid being dispensed from the valve.

[0048] Despite the variation in valve OPENING voltage, the accuracy of the
flow rate of fluid delivered from the fluidic delivery device may be
stabilized or maintained over its lifetime by minimizing the valve
OPENING time (i.e., the time it takes to the charge applied across the
piezoelectric actuator to go from 0V to the opening voltage 302) to
insure that the valve opens quickly. FIGS. 3g-3n illustrate this concept
by depicting two different valve OPENING times. A first exemplary valve
OPENING time is shown in FIGS. 3g-3j, while a second exemplary valve
OPENING time is shown in FIGS. 3k-3n. The valve OPENING time in FIGS.
3k-3n is greater than that shown in FIGS. 3g-3j. As a result, the slope
of the waveform in FIGS. 3k-3n is smaller (i.e., less steep) than that
shown in FIGS. 3g-3j. Over time the valve OPENING voltage (reference
element 302 in FIGS. 3j and 3n) will increase due to drift of the valve
and piezoelectric actuator as represented by reference element 302'. At
the valve OPENING voltage 302', the valve OPENED time in FIGS. 3g, 3k is
reduced to that shown in FIGS. 3h, 3l, respectively, thereby compromising
the accuracy of the flow rate delivered by the valve. Initially, the
deviation or error due to reduced valve OPENED time resulting from this
increase in valve OPENING voltage may be negligible, but over the
lifetime of the valve OPENING voltage will continue to rise and
eventually may result in a significant underdosage in the amount of fluid
delivered. The relatively large valve OPENING time of the example in
FIGS. 3k-3n reduces the valve OPENED time from that shown in FIG. 3k to
that shown in FIG. 3l by an amount identified as "Error on one Valve
OPENED time" (FIG. 3k). It has been recognized that reducing or
minimizing the valve OPENING time (as represented by the graphical
waveform in FIGS. 3g-3j in comparison to that shown in FIGS. 3k-3n)
minimizes any reduction in valve OPENED time, as identified by the
smaller "Error on one Valve OPENED time" shown in FIG. 3g compared to
that in FIG. 3k. It is therefore desirable to minimize the valve OPENING
time in order to minimize the reduction in valve OPENED time resulting
from an increase in valve OPENING voltage over the lifetime of the valve
to stabilize the flow rate.

[0049] The valve OPENING time can be minimized by dividing the PWM charge
input signal for driving the charge pump into multiple PWM units, with
each PWM unit applying for that duration of time its own associated or
corresponding set of PWM parameters (e.g., frequency, duty cycle, and
duration for which the PWM charge input signal should be generated
(transistor ON time/transistor OFF time)). It is contemplated and within
the scope of the present invention for each of the multiple PWM units to
be equal or non-equal, as desired. There is an optimum number of PWM
units that may be determined for the particular piezoelectric actuator
for minimizing the valve OPENING time. On the one hand, if the number of
PWM units is less than the optimum number of PWM units then the minimum
valve OPENING time will not be realized. On the other hand, if the
optimum number of PWM units is exceeded, no further reduction in valve
OPENING time will be realized.

[0050] An exploded view of a single PWM charge input signal (reference
element 307 from FIG. 3d) is shown in FIG. 3f. In the example shown in
FIG. 3f, the PWM charge input signal is divided into 20 PWM units each
having is own associated PWM parameters. The 20 PWM units together for a
single block are referred to as a PWM group (PWM charge input signal). At
the beginning of each block (e.g., 400 second duration block) the PWM
charge input signal is generated to drive the charge pump. The graphical
representation shown in FIG. 3d shows the PWM charge input signal driving
the charge pump until the voltage applied across the piezoelectric
actuator 53 reaches the 60V predetermined threshold voltage (reference
element 301 in FIG. 3c) necessary to displace the piezoelectric actuator
and thus open the valve 115. When the voltage applied across the
piezoelectric actuator 53 reaches the 60V predetermined threshold voltage
the PWM charge input signal is cut off or ended by the processor 640
(FIG. 4). At the end of the valve OPENED time in FIG. 3a, a discharge
signal is generated (FIG. 3b) by the processor 640 and received by the
Voltage Discharge Circuitry 630 causing the voltage stored across the
piezoelectric actuator 53 to drop from 60V to the valve OPENING voltage
(reference element number 302 in FIG. 3c).

[0051] In still another improvement of the present invention, to further
optimize valve OPENING time the transistor ON time and/or OFF time for
each PWM unit of a PWM charge input signal may be adjusted as represented
by the examples shown in FIGS. 5 and 6. For a constant battery voltage,
the time duration for each block (e.g., 400 seconds) is fixed and the
transistor ON time (period of time for which the transistor 620 is ON) is
also fixed, however, the transistor OFF time (period of time for which
transistor 620 is OFF) may vary among the different PWM units in a
particular PWM group (i.e., a particular PWM charge input signal). Since
the maximum current drawn from the power supply 605 is limited, the
transistor ON time is fixed to limit the current drawn. The charge pump
draws current from the power supply 605 when the PWM charge input signal
is generated. The transistor OFF time duration must be sufficient to
insure complete transfer of charges from the inductor 615 that stores the
charge to the piezoelectric actuator 53. Since the time to transfer
charge from the inductor 615 to the piezoelectric actuator 53 depends on
the charge already stored in the piezoelectric actuator 53 at any given
time, the transistor OFF time varies among PWM units within a particular
PWM group.

[0052] In addition, over time, for example, the passing of several years,
the power supply voltage will decrease and thus the amount of charge
built across the inductor 615 will also decrease. It is therefore
advantageous to vary the transistor ON time when the power supply voltage
changes in order to optimize the valve OPENING time. Similarly, the
transistor OFF time may be adjusted in order to allow sufficient time for
charge transfer from the inductor 615 to the piezoelectric actuator 53,
as described in the preceding paragraph,

[0053] FIG. 5 shows an exemplary PWM charge input signal (PWM group)
generated for a single block of 400 seconds duration at a constant power
supply voltage. The exemplary PWM charge input signal (PWM group) shown
is divided into 20 PWM units of equal duration (PWM unit-1, . . . unit-N,
. . . unit-20). The first PWM unit (PWM unit-1) is generated at the
beginning of the 400 second block when the charge across the
piezoelectric actuator 53 is 0V. With each subsequent PWM unit the
voltage across the piezoelectric actuator increases until the
predetermined threshold voltage (e.g., 60V) is applied to the
piezoelectric actuator with the last PWM unit (PWM unit-20). All PWM
units have a constant or fixed transistor ON time duration in which the
PWM charge input signal is generated. The transistor ON time duration is
limited by the current drawn from the power supply (e.g., battery) and
therefore remains constant or fixed among all PWM charge input signals
(PWM groups) and all PWM units within a particular PWM charge input
signal (PWM group). Each PWM unit has a fixed transistor OFF time
duration in which the PWM charge input signal is not generated, however,
the transition OFF time duration may vary among PWM units in a particular
PWM group. As seen in FIG. 5, the transistor ON time for all PWM units is
constant or fixed. The transistor OFF time duration is constant in any
particular PWM unit such as within PWM unit-1, unit-N or unit-20.
However, the transistor OFF time duration varies among PWM unit-1, unit-N
and unit-20. It is clearly shown in FIG. 4 that the transistor OFF time
duration is reduced from PWM unit-1 to PWM unit-20. This adjustment in
the transistor OFF time duration of the PWM signal in any particular PWM
unit takes into account the fact that the charge stored in the
piezoelectric actuator is built up over time. As previously mentioned,
the time necessary to transfer charge from the inductor 615 to the
piezoelectric actuator 53 decreases as the charge stored in the
piezoelectric actuator 53 increase. Accordingly, the transistor OFF time
duration representing the time needed to transfer the charge from the
inductor 615 to the piezoelectric actuator 53 may be reduced.

[0054] FIG. 6 shows exemplary PWM units over a period of time (e.g.,
several years) for depicting a decreasing power supply voltage. Note that
in contrast to that shown in FIG. 5, the PWM units illustrated in FIG. 6
do not represent PWM units within a single PWM group. Instead, what is
represented is three PWM units at different instances of time over
several years. Since the power supply voltage decreases over relatively
long periods of time (e.g., several years) the different PWM units shown
illustrate merely snap shots in time in which the battery voltage
decreases relative to that of an earlier in time PWM unit. In this
example during the time intervals between the PWM units depicted the
battery voltage remains constant or fixed. Referring to FIG. 6, the PWM
units will be addressed from top to bottom. The battery voltage
measurement at the time of the top PWM unit was 3.4V. At some point in
time thereafter, the measured battery voltage dropped to 2.8V
corresponding to the intermediate PWM unit. After the duration of some
period of time thereafter, a battery voltage of 2.4V was measured at the
time of the bottom PWM unit. The transistor OFF time remains constant or
fixed among all PWM groups and all PWM units within a particular PWM
group. However, the transistor ON time is adjusted to account for
decreasing power supply voltage over time. Specifically, the transistor
ON time duration increases as the power supply voltage decreases. The
reasoning for this is because since the power supply voltage decreases
over time then the transistor ON time must increase in order to allow the
same amount of energy relative to when the power source was fully charged
to flow from the power supply 605 to the inductor 615 and subsequently to
the piezoelectric actuator 53. In summary, a longer transistor ON time is
required when the power supply 605 is not fully charged in order to
transfer the same amount of energy from the power supply 605 to the
inductor 615 and subsequently to the piezoelectric actuator 53 then would
be transferred from a power supply 605 having a greater voltage and by
using the same transistor ON time.

[0055] The two concepts presented separately in FIGS. 5 and 6 may be
combined wherein when the power supply voltage remains constant or fixed
the transistor OFF time for a particular PWM unit is adjusted, while the
transistor ON time for a particular PWM unit is adjusted when the power
supply voltage decreases.

[0056] Thus far, the accuracy of the flow rate has been maintained or
stabilized for a particular fluidic delivery device in which the flow
rate may vary over time due to such factors as: (i) mechanical drift over
time, (ii) deformation of the seal with usage over time, and (iii)
depletion of energy provided by the power supply. Accordingly, the
previously described adjustments to the valve OPENING time maintains or
stabilizes the flow rate accuracy for any given fluidic delivery device.

[0057] It is also recognized that the flow rate accuracy may be affected
by parameters that differ from one fluidic delivery device to another.
The flow rate accuracy may be dependent on any number of one or more
factors (hereinafter collective referred to as "fluidic parameters") such
as: (i) the compliance effect, (ii) the maximum flow rate for the given
fluidic delivery device, (iii) the pressure on the fluid in the reservoir
which is dependent on the temperature (temperature-pressure relationship
of reservoir fluid), (iv) valve OPENING time (time for the charge applied
across the piezoelectric actuator to go from 0V to the valve OPENING
voltage, e.g., reference element 302 in FIG. 3c), and (v) valve CLOSING
time (time required to discharge the charge stored across the
piezoelectric actuator from the 60V predetermined threshold voltage
(reference element 301 in FIG. 3c) to the valve OPENING voltage
(reference element 302 in FIG. 3c)). Accordingly, it is desirable to
optimize the accuracy of the flow rate of fluid delivery by compensating
for differences among fluidic delivery devices with respect to any one or
more of these fluidic parameters. Each of these fluidic parameters will
be addressed separately.

[0058] Referring once again to FIG. 1b, the contact disc 38 in the valve
assembly 10 is positioned so that contact ridge 42 aligns with the
disc-shaped seal 26. As piston 16 is pushed upwardly by compression
spring 32, disc-shaped seal 26 is pressed into a sealing contact with
circular contact ridge 42 thereby closing the valve assembly. When the
valve is closed, the elevated or higher pressure from the reservoir 62
compresses the seal 26 downward toward the lower end 20 of bore 14. If
the seal 26 was not made of a compressible material, the volume of fluid
delivered by the fluidic delivery system would correspond to the
graphical representation shown in FIG. 7. It is represented by the
graphical waveform in FIG. 7 that when the valve is in an OPEN state a
constant flow rate (denoted by a graphical waveform having a
substantially constant slope) of fluid is delivered. On the other hand,
while the valve is in a CLOSED state, a fixed or unchanging flow rate is
experienced (as denoted by the substantially horizontal waveform). The
waveform in FIG. 7 transitions directly from a substantially horizontal
waveform to a constant flow rate as represented by that portion of the
waveform having a constant positive slope.

[0059] However, seal 26 is made of a compressible material and hence FIG.
7 fails to take into consideration the fluid dispensed from the valve
when transitioning from the CLOSED state to the OPENED state due to what
is referred to as the compliance effect of the seal. Every time the valve
assembly transitions from a CLOSED state to an OPENED state there is a
transition period before realizing a constant flow rate. This transition
period is denoted by the substantially vertical line (segment "3") shown
in FIG. 8 and hereinafter referred to as a "compliance effect." This
"compliance effect" occurs because the seal 26 is made from a
compressible material, e.g., silicon.

[0060] The compliance effect due to the compressible seal 26 can be
explained by analogy to an air bubble lodged in a valve. FIGS. 9a-9g
depict this air bubble example. In FIG. 9a, the valve is open and the air
bubble is at its lowest pressure. A constant flow rate will be dispensed
from the valve as illustrated by that portion of the graphical waveform
having a substantially constant slope (segment "1"). FIG. 9b shows the
valve immediately after transitioning from an OPENED state to a CLOSED
state. Once the valve is closed a fixed or unchanging flow rate is
experienced (as denoted by the substantially horizontal waveform, e.g.,
segment "2"), as shown in FIG. 9c. While the valve is in this CLOSED
state, pressurized fluid from the reservoir compresses against thereby
reducing in size the air bubble (FIG. 9c). Accordingly, the pressure in
the air bubble is greater when the valve is in a CLOSED state than when
the valve is in an OPENED state. Lastly, FIG. 9d depicts the reopening of
the valve. Since the bubble was in a compressed state when the valve was
closed, upon opening the valve the bubble must first return to its
decompressed or equilibrium state. This decompression is represented by
the vertical portion of the waveform (segment "3") in FIG. 9d. Although
depicted as a vertical segment, in actuality such decompression or
equilibrium occurs extremely quickly over a relatively short period of
time. During decompression undesirably some unaccounted for fluid will be
dispensed from the outlet passage 22 of the fluidic delivery device
thereby compromising the accuracy of the flow rate. Once the pressure has
been equalized, then the fluid will once again be dispensed from the
outlet passage 22 at a substantially constant flow rate, as represented
by the graphical portion of the waveform having a constant slope (segment
"4") in FIG. 9e. This compliance effect is produced each time the valve
transitions from a CLOSED state to an OPEN state. Lastly, FIG. 9f depicts
the transitioning of the valve from the OPENED state to the CLOSED state,
whereby the air bubble is once more compressed in size due to the
pressurized fluid from the reservoir. A fixed or unchanging flow rate is
experienced (as denoted by the substantially horizontal waveform, e.g.,
segment "5"), as shown in FIG. 9g, while the valve is in the CLOSED
state.

[0061] There is no air bubble in a valve assembly. Instead, the air bubble
example shown in FIGS. 9a-9g is merely an illustrative tool for
understanding what in actuality occurs in the valve assembly 10 shown in
FIG. 1b wherein the compressible seal 26 produces a similar compliance
effect. Every valve in which a compressible material is in contact with a
rigid material will result in an analogous compliance effect. The
compressible material, that is, seal 26 in FIG. 1b, is likened to the air
bubble in the example described above in FIGS. 9a-9f. Referring once
again to the graphical waveform depicted in FIG. 8, when the valve is in
an OPENED state seal 26 is at its lowest pressure. A constant flow rate
will be dispensed from the valve as illustrated by segment "1" of the
waveform (FIG. 8) having a substantially constant slope. If the valve is
closed, the pressurized fluid from the reservoir 62 compresses the seal
26 downward into the bore 14. Accordingly, the pressure applied across
the seal 26 is greater when the valve is in a CLOSED state than when the
valve is in an OPEN state. While the valve is closed the flow rate of
fluid dispensed from the valve remains unchanged as represented by the
horizontal portion of the graphical waveform (segment "2") in FIG. 8.
Thereafter, the valve is reopened (segment "4"). Since the seal 26 was in
a compressed state when the valve was closed as a result of the
pressurized fluid in the reservoir, upon opening the valve the seal 26
first returns to its decompressed or equilibrium state. This
decompression is represented by vertical segment "3" of the waveform in
FIG. 8 and depicts the compliance effect. Although depicted as a vertical
waveform, in actuality such decompression or equilibrium occurs extremely
quickly over a relatively short period of time. During decompression of
the seal 26 some accounted for fluid is disadvantageously dispensed from
the outlet passage 22 thereby resulting in an overdosage and compromising
the overall flow rate accuracy. Once the pressure has been equalized,
then the fluid will be dispensed from the outlet passage 22 at a
substantially constant flow rate, once again as represented by segment
"4" of the waveform having a constant slope in FIG. 8. Segment "5" of the
waveform in FIG. 8 shows the valve once again in a CLOSED state as
denoted by the substantially horizontal waveform whereby the seal 26 is
compressed downward due to the pressurized fluid from the reservoir 62.

[0062] The compliance effect resulting from decompression of the seal 26
when transitioning from a CLOSED state to an OPEN state will
disadvantageously dispense an overdosage of fluid relative to the fluid
dosage in the fluid delivery profile programmed by the user. As a result
of this overdosage, the accuracy of the flow rate dispensed from the
fluidic delivery device will be diminished or compromised. The present
invention compensates, corrects or adjusts for the overdosage resulting,
from the compliance effect of the seal 26 thereby improving the flow rate
accuracy of the fluidic delivery device.

[0063] In addition to the compliance effect caused by the compressible
seal 26, other factors may also adversely affect the accuracy of the flow
rate of the fluidic delivery device and may differ among fluidic delivery
devices. One such factor is the maximum flow rate for a given fluidic
delivery device, which is dependent on: (a) the fluidic regulator or
fluidic restrictor, and (b) the differential pressure across the fluidic
regulator or fluidic restrictor. Both of these parameters may differ
among fluidic delivery devices. The fluidic regulator or fluidic resistor
60 (as shown in FIG. 1b) may be selected to achieve a desired flow rate.
As for the differential pressure across the fluidic restrictor, this
value may be determined by subtracting the ambient pressure from the
reservoir pressure. Once again the reservoir pressure may vary among
fluidic delivery devices. Variation in reservoir fluid pressure will
impact the maximum flow rate of fluid delivered by the fluidic delivery
device. Any deviation in maximum flow rate, in turn, will compromise the
accuracy of the programmed flow rate of the fluid being dispensed from
the fluidic delivery device.

[0064] Yet another parameter that has an impact on the accuracy of the
flow rate for a particular fluidic delivery device is the dependency.
temperature has on the pressure of the fluid in the reservoir. As the
temperature increases, the reservoir pressure increases, therefore the
flow rate will increase. Here again, any change in flow rate will
diminish the flow rate accuracy of the fluid delivered from the fluidic
delivery device at a programmed fluid delivery profile.

[0065] Any given fluidic delivery device will also have an associated
valve OPENING time (time required for the piezoelectric actuator to reach
the valve OPENING voltage, reference element 302 in FIG. 3c) and valve
CLOSING time (time required for the voltage across the piezoelectric
actuator to drop from the 60V predetermined threshold voltage to the
valve OPENING voltage, reference element 302 in FIG. 3c) that may vary
among fluidic delivery devices. For instance, two fluidic delivery
devices may be programmed to have the same fluid delivery profile but
different valve OPENING voltages (represented by reference element 302 in
FIG. 3c) and associated valve OPENING times. For instance, a first
fluidic delivery device may have a valve OPENING voltage of 57V while a
second fluidic delivery device has a valve OPENING voltage of 55V. A
longer valve OPENING time (i.e., time for charge across the piezoelectric
actuator to reach the valve OPENING voltage) will be required for the
first fluidic delivery device to reach the associated first valve OPENING
voltage of 57V in comparison to the valve OPENING time for the second
fluidic delivery device needed to attain the associated second valve
OPENING voltage of 55V. The longer the valve OPENING time required to
reach the associated valve OPENING voltage, the longer the time needed
for the valve to remain in a valve OPENED state. Accordingly, transistor
620 in FIG. 4 will have to be driven (e.g., switched ON/OFF) by the PWM
charge input signal for a longer duration of time. In summary, the valve
OPENED time varies as a direct function of the valve OPENING time. That
is, as the vale OPENING time increases, the duration of time for which
the valve needs to remain in an OPENED state to reach the predetermined
threshold voltage of 60V also increases. Therefore, if the time for which
the valve needs to remain in an OPENED state is not adjusted or
compensated for accordingly depending on the valve OPENING voltage and
associated valve OPENING time for the particular fluidic delivery system,
then undesirably an underdosage of fluid will be dispensed or delivered
thereby comprising the accuracy of the flow rate.

[0066] The present invention optimizes the flow rate accuracy of the
fluidic delivery device by compensating for any one or more of these
fluidic parameters. During manufacture of the valve assembly, one or more
fluidic parameters (e.g., compliance effect, maximum flow rate,
temperature-pressure relationship of reservoir fluid, valve OPENING time,
and valve CLOSING time) that could have an impact on the accuracy of the
flow rate is quantified or calibrated preferably for each particular
valve assembly. Alternatively, instead of calibrating one or more fluidic
parameters for each valve assembly a constant or fixed calibrated value
may otherwise be used for all valve assemblies resulting in a less
accurate flow rate. As still another alternative to specifically
calibrating the fluidic parameter, an approximation may be utilized by
relying on other known parameters that need not be calibrated.
Hereinafter these fluidic parameters calibrated at the time of
manufacture are collectively referred to as the "calibrated fluidic
parameters" and stored in a memory associated with the fluidic delivery
device, preferably a non-volatile memory such as a FLASH memory,
described in detail below.

[0067] Specifically, the compliance effect for a particular valve assembly
may be quantified or calibrated by measuring the change in weight of
delivered fluid from the valve assembly (Δy of segment "3" in FIG.
8) as a result of the compliance effect when transitioning the valve from
a CLOSED state to an OPENED state. Alternatively, instead of measuring
the weight of the dispensed fluid, the volume may be monitored based on
the time needed to fill a predefined volume when operating at a constant
flow rate. In either case, the weight or volume of the fluid dispensed as
a result of the compliance effect due to the seal 26 can be quantified
through testing and stored in memory. The maximum flow rate may be
calibrated by merely operating the valve and monitoring how long it takes
to fill a predefined volume. A temperature-pressure relationship of the
reservoir fluid may be established by monitoring the pressure of the
fluid in the reservoir while varying the temperature. Lastly, the valve
OPENING time of the valve assembly is dependent on the valve OPENING
voltage and may be calibrated by monitoring the period of time it takes
the piezoelectric actuator to reach the valve OPENING voltage. The
present invention is not limited to these described methods for
ascertaining the calibrated fluidic parameters and other methods are
contemplated. As previously mentioned, once calibrated, these fluidic
parameters are stored in memory, preferably a non-volatile memory,
associated with the fluidic delivery device.

[0068] Using a control device a user (e.g.; patient, clinician,
technician, nurse, physician) programs the fluidic delivery device to
dispense a fluid over time based on a programmed fluid delivery profile.
The fluid delivery profile is preferably for a 24 hour period subdivided
into one or more time intervals, each time interval being a multiple of
one hour increments of desired duration. Each time interval is preferably
less than or equal to a maximum time interval (preferably 24 hours) but
greater than or equal to a minimum time interval (preferably one hour).
For instance, the 24 hour fluid delivery profile may be subdivided into
24 time intervals, each time interval 1 hour in duration. Alternatively,
the 24 hour fluid delivery profile may be subdivided into 4 time
intervals, each time interval 6 hours in duration. Still yet another
exemplary 24 hour fluid delivery profile may comprise only 2 time
intervals, the first time interval being 1 hour in duration, while the
last time interval is 23 hours. As is evident from these examples, the 24
hour fluid delivery profile may be subdivided so that the time intervals
are of equal or unequal duration. Furthermore, the minimum time interval
and maximum time interval may also be programmed, as desired. In addition
to the time intervals, the user also programs the concentration and
delivery rate of the fluid to be delivered by the fluidic delivery
device.

[0069] Once a fluid delivery profile has been programmed or configured by
a control device communication is established, preferably via a wireless
communication interface, with the fluidic delivery device. Initially, the
control unit reads any one or more of the calibrated fluidic parameters
stored in a non-volatile memory device associated with the fluidic
delivery device. The control device calculates, for each time interval of
the 24 hour fluid delivery profile, two values. A first value referred to
as an Integer Compensated Valve OPENING Time Per Block (e.g., 400 second
block) over a particular time interval. The second value computed is
hereinafter referred to as a Remainder Compensated Valve OPENING Time Per
Hour. For a particular time interval, these two values are calculated by
the control device based on the flow rate programmed by the user over
that particular time interval and one or more calibrated fluidic
parameters.

[0070] An illustrative example will be described wherein the 24 hour
programmed fluid delivery profile is divided into 8 time intervals, each
time interval being 3 hours in duration. The block is set to 400 seconds
in duration, during which a portion of time the valve remains in an
OPENED state and for the remaining portion of time is in a CLOSED state.

[0071] FIG. 10 is an exemplary flow diagram of the steps performed by the
fluidic delivery system (FIG. 11) in adjusting the valve OPENING time
(i.e., time needed for the piezoelectric actuator to reach a valve
OPENING voltage, reference element 302 in FIG. 3c) to compensate for any
overdosage or underdosage of fluid delivery due to the impact one or more
of the calibrated fluidic parameters. In step 1000, processor 1110
associated with the control device 1105 will determine two values: (i) an
Integer Compensated Valve OPENING Time Per Block and (ii) a Remainder
Compensated Valve OPENING Time Per Hour.

[0072] The Compensated Valve OPENING Time Per Hour is calculated by
performing an Integer operation on the summation of Compensation
Components associated with any one or more of the fluidic parameters. The
Compensated Valve OPENING Time Per Hour compensating for all five fluidic
parameters is represented by the Equation (1) below:

programmed flow rate--is programmed by the user (e.g., physician,
technician, nurse, patient). This value may be entered by the user
directly as a predetermined volume/day (e.g., mL/day) or indirectly as a
weight to be delivered/day (e.g., mg/day), whereby the programmed flow
rate may be determined by dividing the weight to be delivered per day by
the specified drug concentration level programmed by the user. calibrated
maximum flow rate--calibrated at the time of manufacture of the fluidic
delivery device and stored in the non-volatile memory associated with the
fluidic delivery device. The maximum flow rate represents the flow rate
delivered by the valve when continuously open (e.g., see FIG. 2a).
Typically, the maximum flow rate is in the range of approximately 3.7
mL/day--4.3 mL/day). Duration of Block--is the duration of time in which
the valve is opened once and closed once (e.g., 400 seconds).

[0076] The next three Compensations Components (e.g., Valve OPENING Time
Compensation Component, Valve CLOSING Time Compensation Component and
Compliance Effect Compensation Component) in Equation (1) will now be
addressed together. Each of these three Compensation Components may be
specifically calibrated for each fluidic delivery device. With negligible
compromise to the accuracy of the flow rate, rather than specifically
calibrating each of these three Compensation Components for each fluidic
delivery device, a constant value may be established for each of these
three Compensation Components and utilized for all fluidic delivery
devices. Yet a third approach may be employed as an alternative to
specifically calibrating the three Compensation Components for each
fluidic delivery device, whereby a known value is used as the
Compensation Component. For instance, the rise time for the charge
applied across the piezoelectric actuator to reach the predetermined
threshold voltage of 60V is a known value with negligible difference
compared with the calibrated valve OPENING time and thus may be utilized
as the calibrated valve OPENING time to eliminate having to perform this
additional calculation. Each of these three Compensation Components are
also stored in a non-volatile memory associated with the fluidic delivery
device at the time of manufacture. It is noted that the compliance effect
will result in an overdosage of fluid delivered by the fluidic delivery
device and thus the Compliance Effect Compensation Component is a
negative value to reduce the valve OPENING time, while the valve OPENING
time and valve CLOSING time will result in an underdosage so the
respective Compensation Component for each is a positive value.

[0077] Referring once again to Equation (1) the last fluidic component to
be addressed is the Temperature-Pressure Relationship Compensation
Component. At the time of manufacture, the temperature-pressure
relationship of fluid in the reservoir is characterized to determine its
impact on the flow rate and a temperature dependent function is
established as the Temperature-Pressure Relationship Compensation
Component.

[0078] The other value calculated by the control device is the Remainder
Compensated Valve OPENING Time Per Hour by performing a MODULUS
mathematical operation on (summation of the Compensation Component for
one or more of the fluidic parameters, each Compensation Component being
multiplied by the Number of Blocks in One Hour), Number of Blocks in One
Hour). The Remainder Compensated Valve OPENING Time Per Hour compensating
for all five fluidic parameters is represented by the Equation (2) below:

Remainder Compensated Valve OPENING Time Per Hour=MOD ((((Maximum Flow
Rate Compensation Component)*Duration of the Block*Number of Blocks in
One Hour)+(Valve OPENING Time Compensation Component*Number of Blocks in
One Hour)+(Valve CLOSING Time Compensation Component*Number of Blocks in
One Hour)+(Temperature-Pressure Relationship Compensation
Component*Number of Blocks in One Hour)), Number of Blocks in One Hour)
Equation (2)

[0079] The same variables in Equation (2) were also found in the Equation
(1) and described above when calculating the Integer Compensated Valve
OPENING Time Per Block and thus need not be described further.

[0080] In step 1010 of FIG. 10, the Integer Compensated Valve OPENING Time
Per Block and the Remainder Compensated Valve OPENING Time Per Hour
calculated by the control device are transmitted to the fluidic delivery
device via a communication interface. The fluidic delivery device
receives the Integer Compensated Valve OPENING Time Per Block and applies
it to every block in that time interval. However, in step 1020 the
Remainder Compensated Valve OPENING Time Per Hour is distributed by the
fluidic delivery device to those blocks within one hour such that it is
as uniform as possible wherein the time distributed to any particular
block is a whole number (non-negative integer) of one or more seconds. On
the one hand, if the Remainder Compensated Valve OPENING Time Per Hour is
a whole number that is equally divisible among the total number of blocks
in one hour without a remainder then the Remainder Compensated Valve
OPENING Time Per Hour is divided by the number of blocks per hour and
distributed equally to each block. On the other hand, if the Remainder
Compensated Valve OPENING Time Per Hour is a whole number that is not
equally divisible among the total number of blocks in one hour without a
remainder, it is distributed as uniformly as possible as a whole number
of one or more seconds among less than all the blocks within the one
hour. For each block within one hour over the given time interval, in
step 1030, the Total Compensated Valve OPENING time is computed by adding
the Integer Compensated Valve OPENING Time Per Block plus, if distributed
to that particular block, the Remainder Compensated Valve OPENING time
per hour.

[0081] By way of example, the valve OPENING time will be compensated for
only three of the four fluidic parameters, namely, compliance effect,
maximum flow rate and valve OPENING time/valve CLOSING time. The
temperature-pressure dependency of the fluid in the reservoir is not
compensated for in this example.

[0082] One hour of time is divided into 9 blocks, each block 400 seconds
in duration.

[0083] Control device 1105 retrieves from the non-volatile memory (e.g.
FLASH memory) associated with the fluidic delivery device three
calibrated parameters: compliance effect, maximum flow rate and valve
OPENING time. These values are processed by the control unit to generate
an Integer Compensated Valve OPENING Time Per 400 Second Block calculated
using the following equation:

[0085] The Valve Net Compensation Component in this example represents the
summation of the Valve OPENING Time Compensation Component, the Valve
CLOSING Time Compensation Component and the Compliance Effect
Compensation Component. In this example each of these three Compensation
Components is represented as a constant value, rather than being
specifically calibrated for each fluidic delivery device, and thus have
been combined into a single constant value referred to as Valve Net
Compensation Component.

[0086] Assuming the programmed flow rate is 0.5 mL/day, the calibrated
maximum flow rate is 3.95 ml/day and the calibrated Valve Net
Compensation is 5 seconds, then the calculated Integer Compensated Valve
OPENING Time Per 400 Second Block=Integer ((0.5/3.95)* 400+5)=55 seconds.
The Remainder Compensated Valve OPENING Time Per Hour=MOD
(((0.5/3.95)*400*9)+(5*9)), 9)=5 seconds. Since the Remainder Compensated
Valve OPENING Time Per Hour of 5 seconds is not evenly divisible by 9
(the number of 400 second blocks in one hour), then the 5 seconds will be
distributed in one second intervals over the 9 blocks as uniformly as
possible. Specifically, the 5 seconds will be uniformly distributed
across 5 out of the 9 blocks over one hour so each of the 5 blocks has an
additional one second. The Total Compensated Valve OPENING Time Per Hour
is then determined for each of the 9 blocks over one hour based on the
Integer Compensated Valve OPENING Time Per Block (applied to each block)
and the Remainder Compensated Valve OPENING Time Per Hour (if distributed
to that particular block). A Total Compensated Valve OPENING Time for 4
of the 9 blocks will be set to 55 seconds while 5 of the 9 blocks will be
set to 56 seconds (55 seconds+1 second).

[0087] In another example, the Integer Compensated Valve OPENING Time Per
Block is calculated as 111 seconds and the Remainder Compensated Valve
OPENING Time Per Hour is 9 seconds. Since the Remainder Compensated Valve
OPENING Time Per Hour (e.g., 9 seconds) is evenly divisible without a
remainder by the number of blocks per hour (9 blocks), each of the 9
blocks in one hour will have a Remainder Compensated Valve OPENING Time
Per Hour of 1 second. Thus, each of the 9 blocks over one hour will have
a Total Compensated Valve OPENING time of 112 seconds (111 seconds+1
second).

[0088] The invention described thus far is directed to improving the
accuracy of the programmed flow rate for a fluidic delivery device. In
keeping with this goal it is important to monitor any inconsistencies in
programming of the fluidic delivery device. To mitigate the risk of
incorrectly programming the fluidic delivery device, the control unit
preferably verifies the consistency of the data transmitted to the
fluidic delivery device before programming the fluidic delivery device.
As discussed in detail above, the Integer Compensated Valve OPENING Time
Per Block (Equation (1)) and Remainder Compensated

[0089] Valve OPENING Time Per Hour (Equation (2)) are both calculated by
the control device based on the fluidic calibration parameters stored in
a non-volatile memory associated with the fluidic delivery device. The
source code programming steps for each of these two equations is provided
twice or duplicated in the programming code for processor 1110 (FIG. 11).
The first iteration or calculation of Equations (1) and (2) is performed
using a first portion of the programming source code. Before programming
the fluidic delivery device, the control device verifies that these same
two values are obtained by recalculating Equations (1) and (2) using
source code programming steps set forth in a second portion of the
programming source code, different from the first portion. This redundant
processing mitigates the risk of a programming failure by verifying the
flow data integrity prior to transmission.

[0090] In order to further reduce the risk of incorrectly programming the
fluid delivery device, additional checks may be performed using a
specific memory architecture as shown in FIG. 11 for the fluidic delivery
system 1100. System 1100 includes an implantable drug infusion delivery
device 1120 programmed by an external control device 1105 via a wireless
communication interface. Implantable drug infusion delivery device 1120
includes three controllers or processors 1125, 1130, 1135, however, any
number of one or more controllers or processors may be used, as desired.
Each controller has associated therewith a volatile memory device such as
a RAM and a non-volatile memory device, for example, a FLASH memory. A
first, primary or main controller 112 has a volatile RAM memory 145 and a
non-volatile FLASH memory 1150. Any number of one or more secondary or
auxiliary controllers may be included. In the example, there are two
secondary or auxiliary controllers, e.g., a second controller 1130 and a
third controller 1135. Similar to the primary, first or main controller
1125, each secondary or auxiliary controller 1130, 1135 also has a
volatile RAM and a non-volatile FLASH memory. Also associated with the
implantable drug infusion delivery device 1120 but external to the
controllers 1125, 1130, 1135 is a non-volatile EEPROM 1140 electrically
connected to the main controller 1125.

[0091] The calibrated fluidic parameters (e.g., compliance effect, maximum
flow rate, temperature-pressure relationship of reservoir fluid and
opening voltage rise time) are stored in the non-volatile FLASH memory
1150 associated with the main controller 1125. The values calculated by
the control device (e.g., the Integer Compensated Valve OPENING Time Per
Block and the Remainder Compensated Valve OPENING Time Per Hour) are
received by the implantable drug infusion delivery device 1120 and stored
in the non-volatile EEPROM memory 1140 associated therewith.

[0092] During self-testing, preferably once a day, the implantable drug
infusion delivery device 1120 calculates a FLASH code memory CRC and
compares this calculated value with the FLASH code memory CRC that was
previously stored in the FLASH memory 1150 when the implantable drug
infusion delivery device 1120 was programmed during manufacturing. If the
calculated CRC doesn't match with the previously stored CRC value for the
FLASH code memory, then a FLASH code error is set, an alarm is engaged
and delivery of the drug ceases. This process allows checking for
corruption of the fluid calibration parameters stored in the non-volatile
FLASH memory 1150.

[0093] In order to minimize power consumption, the main controller 1125 is
powered off until awakened when required to perform processing. Whenever
the main controller wakes up it copies the entire contents of the
non-volatile EEPROM memory 1140 to volatile RAM memory 1145. When reading
the contents of the EEPROM memory 1140, the main controller 1125
calculates the EEPROM checksum and verifies it with the previously stored
checksum in the EEPROM memory. If the calculated checksum doesn't match
with the previously stored checksum in the EEPROM, then the EEPROM error
code is set, an alarm is engaged and drug delivery ceases. Such
verification processing will detect corruption of the fluid delivery
profile since the Integer Compensated Valve OPENING Time Per Block and
the Remainder Compensated Valve OPENING Time Per Hour for every time
interval comprising the fluid delivery profile is stored in EEPROM memory
1140.

[0094] Upon a reset event triggered by any of the controllers, the other
secondary controllers (other than the main controller 1125) also copy the
drug delivery profile data from the EEPROM 1140 into their respective
associated RAM, either via a direct path (e.g., EEPROM directly to RAM
associated with secondary controller) or through an indirect path (e.g.,
EEPROM to RAM associated with main controller to RAM associated with
secondary controller).

[0095] As explained above, the EEPROM 1140 and the secondary controllers
(other than the main controller 1125) commonly store the same drug
delivery profile data in their respective RAM memories. The drug delivery
profile data is stored in the EEPROM 1140 of the main controller 1125
because it receives the information from the control device 1105. For
instance, the main controller 1125 programs the second controller 1130
with the same drug delivery profile, because the second controller 1130
drives the valve. The same drug delivery profile is stored in the third
controller 1135 as well. During daily self-testing of the implantable
drug infusion delivery device 1120, the drug delivery profile data is
stored in the EEPROM 1140 as well as in the volatile RAM associated with
each of the controllers. If during self-testing there is a discrepancy
between the drug profile data stored in EEPROM 1140 and that stored in
any of the volatile RAMs of any of the controllers, an alarm will be
activated and drug delivery will cease.

[0096] Any of the previously described methods may be employed separately
or used in any combination thereof for mitigating the risk of delivery of
the fluid from the fluidic delivery device at an incorrect flow rate. In
the first instance, the fluid delivery profile data is verified prior to
programming the fluidic delivery device, whereas the second additional
method checks the consistency of the fluid delivery device profile stored
in the memory associated with the fluidic delivery device, preferably at
least once a day.

[0097] Thus, while there have been shown, described, and pointed out
fundamental novel features-of the invention as applied to a preferred
embodiment thereof, it will be understood that various omissions,
substitutions, and changes in the form and details of the devices
illustrated, and in their operation, may be made by those skilled in the
art without departing from the spirit and scope of the invention. For
example, it is expressly intended that all combinations of those elements
and/or steps that perform substantially the same function, in
substantially the same way, to achieve the same results be within the
scope of the invention. Substitutions of elements from one described
embodiment to another are also fully intended and contemplated. It is
also to be understood that the drawings are not necessarily drawn to
scale, but that they are merely conceptual in nature. It is the
intention, therefore, to be limited only as indicated by the scope of the
claims appended hereto.

[0098] Every issued patent, pending patent application, publication,
journal article, book or any other reference cited herein is each
incorporated by reference in their entirety.

Patent applications by Alec Ginggen, Plymouth, MA US

Patent applications by Rocco Crivelli, Neuchatel CH

Patent applications by Toralf Bork, Enges CH

Patent applications by Codman Neuro Sciences Sarl

Patent applications in class Implanted dynamic device or system

Patent applications in all subclasses Implanted dynamic device or system